Plasma treatment apparatus and surface treatment apparatus of substrate

ABSTRACT

A plasma treatment apparatus of the present invention comprises: a plasma generation chamber  34  for activating gas supplied thereto so as to generate plasma; a depressurization chamber  50  which is connected to the plasma generation chamber  34  and which accommodates a member  52  to be plasma-treated; and a diffuser  58  which is provided at a joint part of the plasma generation chamber  34  and the depressurization chamber  50,  which guides the plasma in a direction inclined to a gas flow path of the plasma generation chamber  34,  and which introduces the plasma into the depressurization chamber  50  while diffusing the plasma in the depressurization chamber  50.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma treatment apparatus capable ofuniformly treating a surface of a substrate having a larger area than across sectional area of a plasma introductory part, and a surfacetreatment apparatus for treating a surface of a substrate by a gasplasma.

2. Description of Related Art

According to a semiconductor apparatus and an OLED (organic lightemitting diode) display in which a conductive thin film formed on asubstrate, a surface of the conductive thin film is plasma-treated so asto improve or stabilize properties thereof.

In the OLED display, a thin film containing a fluorescent orphosphorescent organic chemical compound is sandwiched between an anodeelectrode and a cathode electrode. In the OLED display, positive holesand electrons are injected into the thin film from the anode electrode'sside and the cathode electrode's side, respectively, so as to recombinethem. Due to energy that is discharged by this recombination, thefluorescent or phosphorescent organic chemical compound is excited toemit light. Accordingly, it is preferable to deposit a plurality ofchemical compounds so that ionized potential (Ip) is made smaller fromthe anode electrode's side toward the cathode electrode's side.

In addition, in order to enhance a work function of the anode electrodeand improve injection of the positive hole, it has been known that asurface of the anode electrode is treated by UV-O₃, O₂ plasma, the like(see patent document 1, for example).

FIG. 5 is a perspective view of a substantial part of a structure of anOLED display during manufacture, and FIG. 6 is sectional view of asubstantial part of the OLED display taken on a line of A-A of FIG. 5.In the drawings, a reference numeral 10 denotes an insulating substratesuch as glass, and reference numerals 12 a and 12 b denote a pair ofthin film transistors formed on the insulating substrate 10. Althoughnot shown in the drawings, many thin film transistors are formed in theform of a matrix. A reference numeral 14 denotes a layer that isconnected to an electrode through which a main electric current of thethin film transistor 12 a passes, for example, a drain electrode wiringlayer that is connected to a drain electrode. On the insulatingsubstrate 10, except for the thin film transistor 12 a, a sourceelectrode wiring layer through which the main electric current passes, apower source wire, a grounding wire, and a gate electrode wire of thethin film transistor 12 b are formed, however, they are omitted in thedrawings.

A reference numeral 16 denotes a resin insulating layer which coats thesurface of the insulating substrate 10 so as to smooth out theirregularities of the surface of the insulating substrate 10 which arecaused by the thin film transistor 12 or the like. The resin insulatinglayer 16 is formed from an acrylic transparent resin, for example. Areference numeral 18 denotes a through hole that is formed in a portionof the resin insulating layer 16. A diameter of the through hole 18 ismade smaller from an opening top toward a bottom, and the drainelectrode wiring layer 14 is exposed at its bottom. Reference numerals20 a and 20 b denote electrode wiring layers formed on the resininsulating layer 16, respectively. The electrode wiring layer 20 a isconnected to a power source (not shown), while the other electrodewiring layer 20 b is electrically connected to the drain electrodewiring layer 14 at the bottom of the through hole 18. Therefore, theelectrode wiring layer 20 b and the thin film transistor 12 a areelectrically connected through the drain electrode wiring layer 14. Areference numeral 22 denotes an edge insulating layer which coats thesurface of the resin insulating layer 16. In the edge insulating layer22, a portion of the electrode wiring layer 20 a is exposed through awindow 22 a to form an anode electrode 24 and to form a window 22 b atthe through hole 18. A reference numeral 26 denotes resin depositedlayers that are placed opposite to each other and that sandwich an areaincluding the anode electrode 24 and the through hole 18, and theiropposed walls are inversely tapered.

In FIG. 6, a reference numeral 28 denotes an OLED layer formed on theanode electrode 24 and the OLED layer 28 is formed through a metallicmask (not illustrated). In addition, an opening of the resin depositedlayer 26 is used as a portion of the mask and an end of the OLED layer28 is spaced apart from a base portion of the resin deposited layer 26.A reference numeral 30 denotes a cathode electrode wiring layer formedthrough a metallic mask (not shown) on the OLED layer 28 and the resininsulating layer 16 except for an anode electrode wiring layer 20.Further, the cathode electrode wiring layer 30 is formed using theopening of the resin deposited layer 26 as a portion of the mask, and aportion of the cathode electrode wiring layer 30 which overlaps the OLEDlayer 28 is formed as a cathode electrode 32. This cathode electrodewiring layer 30 is connected to the drain electrode wiring layer 14formed on the insulating substrate 10 through the through hole 18 formedin the edge insulating layer 22.

Further, the OLED display shown in FIG. 6 is hermetically sealed byputting the transparent glass substrate thereon. The OLED display isused as a light emitting apparatus or a display unit by releasing thelight emitted from the OLED layer 28 from the transparent glass throughthe cathode electrode wiring layer 30. Such OLED display is called atop-emission OLED display. In the top-emission OLED display, the lightemitted from the OLED layer 28 to the anode electrode 24 is reflected onthe surface of the anode electrode 24 so as to enhance the brightness.

In this display unit, the anode electrode 24 functions as a source forinjecting positive holes into the OLED layer 28 and is associated withefficiency of light emission of the OLED layer 28. Accordingly, as amaterial of an electrode, a material having a large work function isdesired.

In order to effectively release the light emitted from the OLED layer28, a material with high reflectivity is selected for the anodeelectrode wiring layer 20 and the anode electrode 24. For example, AlNdor the like is used.

Thus, it is preferable to form the anode electrode 24 from an electrodematerial satisfying different properties of the working function and thereflectivity. However, there is no material that satisfies the bothproperties at the same time and that can be easily handled. Furthermore,in even a proper electrode material, effects of the material may varydepending on its surface condition. ITO and Nickel inherently have largework functions, so that positive holes can be injected therein very wellonly by cleaning their surfaces through a cleaning processing and thenoxidizing the surfaces. However, a drawback to the ITO and Nickel is lowreflectivity. In the meanwhile, aluminum and aluminum base alloy havehigh reflectivity and can be easily handled. However, their workingfunctions are small, so that it is necessary to form a functionalorganic film after the cleaning processing in order to enhance theirworking functions.

For this reason, in the structure during manufacture shown in FIG. 5,the surface of the anode electrode 24 is cleaned before forming the OLEDlayer 28. Such cleaning enhances the working function and thereflectivity of the anode electrode 24. Further, in order to increasethe working function, an functional organic film is formed on thecleaned surface of the electrode. For example, cleaning process iscarried out by ozone UV-O₃ which is generated by applying ultravioletrays to a substrate to be surface-treated in oxygen atmosphere. In thecleaning using ozone UV-O₃, there are few damages in the resinstructures 16, 22, and 26 located at the edge of the anode electrode 24.However, since the functional organic film cannot be formed on thesurface of the electrode in succession from the cleaning operation, anadditional equipment is needed.

On the contrary, a plasma treatment apparatus does not require anyadditional equipment. In the plasma treatment apparatus, the surface ofthe electrode can be cleaned by oxygen plasma and a functional organicfilm can be formed on the cleaned surface of the electrode by using adifferent material gas. In a typical parallel flat plate type plasmatreatment apparatus, two parallel electrodes are placed opposite to eachother in a depressurization chamber and a substrate is provided betweenthe parallel electrodes. When high-frequency power is applied betweenthe parallel electrodes, gas in the depressurization chamber is reactedand thus plasma is generated. As far as the structure of the apparatusis simple and the substrate can be provided between the parallel plateelectrodes, even a large substrate can be uniformly treated.

In an ECR plasma treatment apparatus, high-density plasma is generatedby adding a micro wave and a magnetic filed from an electromagnet in aplasma generation chamber connected to the depressurization chamber andsetting intensity of the magnetic field in such a manner that anelectron cyclotron resonance condition is satisfied. In the ECR plasmatreatment apparatus, a large substrate can also be treated.

[Document 1] Japanese Unexamined Patent Publication No. (Patent KokaiNo.) 08-167479 (1996) (See paragraph [0013]) However, since a portion ofcoating resin such as the resin insulating layer 16 and the edgeinsulating layer 22 is exposed when the anode electrode 24 is cleaned,the surface of the coating resin is exposed to plasma. The surface ofthe coating resin is ruined if the high-density plasma is allowed todirectly contact the surface. Particularly, if the surface of thecoating resin near the anode electrode 24 is ruined, a portion of theresin that is scraped thereby adheres to the surface of the anode, andbrightness of this portion may be lowered or this portion may not emitlight (thus, a dark spot is formed). This dark spot portion is enlargedwith time. Such enlargement of the dark spot area is accelerated byblinking, and at last, the all the pixels do not emit light. Thus, thisexerts adverse effects on a display quality and reliability.

In the meanwhile, if cleaning of the surfaces of the electrodes formedon the substrate and forming the functional organic film on theelectrode surfaces are sequentially carried out using a singleapparatus, foreign matter is generated by reaction with plasma gas anddeposited in a chamber. Thus-deposited functional organic film materialis decomposed during the cleaning process and then adheres to the anodeelectrode again. Therefore, it is necessary that such deposit isperiodically removed from depressurization chamber.

For such a reason, while the structure of the parallel flat plate typeplasma treatment apparatus is simple, there are many problems in bothcarrying out the cleaning of the surfaces of the electrodes and formingthe functional organic film on the electrode surface using the sameapparatus.

On the contrary, in the ECR plasma treatment apparatus, high-densityplasma generated at a plasma generation source is diffused in thedepressurization chamber in which the substrate is provided so as toexpose the substrate to such plasma. Therefore, the ECR plasma treatmentapparatus can prevent the damage of the coating resin. However, sincethe plasma introductory part of the depressurization chamber is awayfrom the substrate, if the opening diameter of the plasma introductorypart is small, the plasma introduced in the depressurization chamber isscattered in all directions. Therefore, the electrodes on the flatsubstrate cannot be uniformly treated in the ECR plasma treatmentapparatus and the unevenness of the treatment is severe in the largesubstrate.

Therefore, plasma to be introduced in the depressurization chamber isdiffused by a diffuser (a diffusion plate) to realize a uniformtreatment. Many diffusers have been manufactured by way of trial undervarious conditions by changing a hole diameter and a space between theholes, for example, and the treatment states have been observed.However, such conventional diffusers cannot solve a big difference in acleaning level of the electrodes between a center portion and a marginalarea of a large substrate. In addition, the ECR plasma treatmentapparatus requires an electromagnet and advanced control apparatus, sothat the apparatus has a complicated structure and is expensive.

As a plasma treatment apparatus in which a plasma generation source isconnected to a depressurization chamber, there is an apparatus using aninductive coupled plasma (ICP) for generating plasma by a high-frequencyelectric field. This apparatus is cheaper than the ECR plasma treatmentapparatus. However, this apparatus has the same problem as the ECRplasma treatment apparatus because the plasma introductory part of thedepressurization chamber is away from the substrate.

Further, it is also conceivable that a plurality of plasma generationsources are provided in one depressurization chamber and plasma isdiffused on one substrate from each plasma generation source. However,it is difficult to control a plurality of plasma generation sourcesunder the same condition. Moreover, maintenance of the apparatus iscomplicated and the cost of equipment is high.

SUMMARY OF THE INVENTION

In order to solve the above problems, we have eventually found thepresent invention. Accordingly, an object of the present invention is toprovide a plasma treatment apparatus which comprises: a plasmageneration chamber for activating gas supplied thereto so as to generateplasma; a depressurization chamber which is connected to the plasmageneration chamber and which accommodates a member to be plasma-treated;and a diffuser which is provided at a joint part of the plasmageneration chamber and the depressurization chamber, which guides theplasma in a direction inclined to a gas flow path of the plasmageneration chamber, and which introduces the plasma into thedepressurization chamber while diffusing the plasma in thedepressurization chamber.

Further, the present invention provides a surface treatment apparatuswhich comprises: a plasma generation chamber for activating gas suppliedthereto so as to generate plasma; a depressurization chamber which isconnected to the plasma generation chamber and which accommodates asubstrate with a conductive thin film and an organic thin film formed ona main surface thereof; and a diffuser which is provided at a joint partof the plasma generation chamber and the depressurization chamber, whichguides the plasma in a direction inclined to a gas flow path of theplasma generation chamber, and which introduces the plasma into thedepressurization chamber while diffusing the plasma in thedepressurization chamber, wherein a surface of the conductive thin filmformed on the substrate is treated using different gas plasma bysuccessively feeding different material gases to the plasma generationchamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of a substantial part of a plasmatreatment system of the present invention.

FIG. 2 is a graph for comparing thicknesses of organic films between aconventional system and a system of the present invention.

FIG. 3 is a sectional side view for showing a shape of an opening end ofa diffuser.

FIG. 4 is a enlarged sectional side view of a substantial part of avariation of the diffuser.

FIG. 5 is a sectional side view of a substantial part of an OLEDdisplay.

FIG. 6 is a perspective view of a substantial part of a structure of theOLED display during manufacture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below withreference to FIG. 1. In FIG. 1, a reference numeral 34 denotes a plasmageneration chamber for generating plasma by activating gas suppliedthereto. In the plasma generation chamber 34, a plurality of gascylinders 36, 38, 40 which is opened and closed by valves 36 a, 38 a,and 40 a are connected through a flow rate controller 42 to a gas inlet34 a which is provided at a lower end of the chamber 34. A referencenumeral 44 denotes an induction coil that is wound around the plasmageneration chamber 34. The induction coil 44 is connected to a highfrequency oscillator 48 through a matching circuit 46. When a highfrequency current flows through the induction coil 44, the gas suppliedin the plasma generation chamber 34 is excited into plasma. A referencenumeral 50 denotes a depressurization chamber. In the depressurizationchamber 50, a gate (not shown) is disposed at a peripheral surfacethereof. The plasma generation chamber 34 is connected to a bottom 50 aof the chamber 50, and the plasma gas is supplied from a plasma inlet(plasma introductory part) 34 b. A reference numeral 52 denotes asubstrate (a member to be plasma-treated) whose surface is coated withresin and in which conductive thin film is provided on a substantialpart of the resin coating. The surface of the conductive thin film iscleaned by contacting it with the plasma gas (a detailed explanation isherein omitted). A reference numeral 54 denotes a substrate supportingmeans for supporting the substrate 52 with the conductive thin filmformation surface down. To the substrate supporting means 54, a movingmechanism 56 for moving the substrate 52 in a horizontal direction, aswinging mechanism for swinging a main surface of the substrate 52 withrespect to a horizontal plane, a rotation mechanism for rotating thesubstrate around a rotational axis perpendicular to the horizontalplane, and heating means for heating the substrate (not shown) or thelike are provided when necessary.

A reference numeral 58 denotes a diffuser that is a characteristic ofthe present invention. The diffuser 58 is provided at a joint part ofthe plasma generation chamber 34 and the depressurization chamber 50 anddiffuses the plasma introduced in the depressurization chamber 50 overthe whole surface of the substrate 52. According to the illustratedexample, two tubular bodies 60 a and 60 b inclined relative to thesurface of the substrate 52 guide the plasma in an inclined direction.One end side of the tubular body 60 a and one end side of the tubularbody 60 b are in intimate contact with each other and are connected tothe plasma inlet 34 b of the plasma generation chamber 34, while theother end sides of the tubular bodies 60 a and 60 b are separated fromeach other. Respective axes a and b shown by a dashed line in thedrawing are extended to the ends of the substrate 52 so that extensionsof the axes a and b intersect with the ends of the substrate 52.Respective axes a and b are inclined at 45 degrees relative to thehorizontal plane, and opening ends c and d of the tubular bodies 60 aand 60 b substantially perpendicularly intersect these axes a and b.Thus, the substrate 52 and the opening ends c and d are not arrangedparallel to each other. The illustrated tubular bodies 60 a and 60 b arecircular in cross section.

A reference numeral 62 denotes a pressure controller for controlling apressure within the depressurization chamber 50, and a reference numeral64 denotes a turbo-molecular pump that is connected to the pressurecontroller 62. A reference numeral 66 denotes a dry pump. The pressurecontroller 62 and the turbo-molecular pump 64 are connected to the drypump 66 through a valve 68 and a valve 70, respectively, so as todepressurize the depressurization chamber 50.

The operation of the above-described plasma treatment apparatus will bedescribed below. First, a substrate (a member to be plasma-treated) 52is prepared. As is the case with the structure of the OLED displayduring manufacture shown in FIG. 6, in the substrate 52, a conductivepattern formed on an insulating substrate is covered with a coatingresin and a portion of the conductive pattern is exposed through awindow formed in a substantial part of this coating resin so as to forma conductive thin film (anode electrode). In the substrate 52, in orderto enhance the working function of the surface of the anode electrodeand increase the efficiency of positive hole injection, the surface ofthe conductive thin film is cleaned and then oxidized, and then acoating made of organic material is formed on the conductive thin film.

This substrate 52 is placed in the depressurization chamber 50 and thenthe chamber 50 is hermetically sealed. The substrate 52 placed in thedepressurization chamber 50 is set at an earth potential or a properbias potential.

Next, the valve 68 is opened to operate the dry pump 66 and todepressurize the depressurization chamber 50. Then, the valve 70 isopened to operate the turbo-molecular pump 64, and the valve 68 isclosed to depressurize the depressurization chamber 50 sufficiently.When the depressurization chamber 50 is sufficiently depressurized, thegas cylinders 36 to 40 are opened or closed selectively by controllingthe opening and closing of the valves 36 a to 40 a, predetermined gas isfed into the plasma generating chamber 34, and the pressure in thedepressurization chamber 50 is maintained at a predetermined value bythe flow rate controller 42. Under such condition, when a high frequencycurrent flows through the induction coil 44 and an induction magnetfield is generated in the plasma generation chamber 34, the material gasis oscillated at a high frequency and thus plasma is generated.

When an oxygen gas is supplied as the material gas, O₂ plasma is fedinto the depressurization chamber 50 through the diffuser 58. Thisoxygen decomposes and removes contamination adhering to the surface ofthe electrode formed on the surface of the substrate 52, and further, itoxidizes the cleaned surface of the electrode.

When the aforementioned operation is completed, a functional organiclayer is formed on the cleaned surface of the conductive thin film.Therefore, the supply of the oxygen gas is stopped, the current flow tothe induction coil 44 is temporarily stopped, and the oxygen gasremaining in the depressurization chamber 50 is discharged. Afterchecking that the pressure is sufficiently decreased and the oxygen gasis sufficiently discharged, a gas to be used as a material for formingan organic film is supplied to the plasma generation chamber 34.

If C_(x)H_(y)F_(z) (x>1, y≧0, z≧2) is used as the gas to be used as amaterial for forming an organic film, a functional organic film that ismainly composed of CF_(x) can be formed on the substrate 52 having theconductive thin film. The gas to be used as a material for forming anorganic film is supplied to the plasma generation chamber 34. When acurrent flows through the induction coil 44 again, plasma gas is fedinto the depressurization chamber 50 through the diffuser 58. On thesurface of the substrate 52 having the conductive thin film on which anorganic layer is formed, the functional organic film is formed.

Thus, by successively treating the substrate 52 using various materialgases, it is possible to perform cleaning of the surface of theconductive thin film and forming the coating resin in onedepressurization chamber without changing the substrate.

When such successive operations are completed, the current flow to theinduction coil 44 is stopped, and the supply of the gas to be used as amaterial for forming an organic film is stopped. After a nitrogen gas issupplied into the depressurization chamber 50 to bring back thedepressurization chamber 50 to the atmosphere pressure, the substrate 52is taken out from the depressurized chamber 50. Then, thedepressurization chamber 50 is hermetically sealed and sufficientlydepressurized, and the gas made by mixing the oxygen gas as a main gaswith an argon gas or the like is fed to the plasma generation chamber34. The depressurization chamber 50 is maintained at a constantpressure, a current is passed through the induction coil 44 so as togenerate plasma, and the generated plasma is supplied to thedepressurization chamber 50 through the diffuser 58.

By conducting such operation, organic films deposited on an inner wallof the plasma generation chamber 34, inner walls of the tubular bodies60 a and 60 b of the diffuser 58, and an inner wall of thedepressurization chamber 50 are decomposed by O₂-plasma gas, and thisdecomposition gas is discharged from the depressurization chamber 50 tothe outside.

After removing the functional organic film in this way, the current flowto the induction coil 44 is stopped, the supply of the oxygen gas or thelike is stopped, the depressurization chamber 50 is brought back to theatmosphere pressure by supplying nitrogen gas thereto, and thedepressurization chamber 50 is opened. After that, a new substrate 52 isput into the depressurization chamber 50 and is subjected to theabove-described operations.

In the plasma treatment apparatus according to the present invention,the cleaning of the substrate 52 in the depressurization chamber 50 byO₂-plasma and the depositing of the organic film on the substrate 52 canbe successively conducted. The organic film adhering to the inner wallor the like of the diffuser during the depositing process can bedecompounded by O₂-plasma and removed from the depressurization chamber50 prior to cleaning a new substrate. Therefore, the operations can berepeated without posing any problem to the cleaning operation of the newsubstrate.

The diffuser 58 is composed of the tubular bodies 60 a and 60 b. Theaxes of the respective tubular bodies 60 a and 60 b are inclinedrelative to the axis of the plasma generation chamber 34. The crosssectional areas of the openings of the respective tubular bodies 60 aand 60 b are smaller than the cross sectional area of the plasma inlet34 b.

Gas is supplied into the plasma generation chamber 34 and thedepressurization chamber 50 is depressurized by the pumps 64 and 66. Forthis reason, there is a pressure gradient in a gas flow path between thediffuser 58, the depressurization chamber 50, and the pump 66.Therefore, the gas supplied to the plasma generation chamber 34 is drawninto the depressurization chamber 50 from the opening end of thediffuser 58 and then diffused in the depressurization chamber 50.

In this time, the gas in the depressurization chamber behaves as anelastic body. Since molecules of the gas repeatedly collide against eachother or against the wall of the chamber, their moving direction ischanged. Accordingly, the gas in the tubular diffuser 58 flows in adirection synthesized from the moving direction controlled by thepressure gradient and the moving direction changed by the collision.

Therefore, the plasma gas generated in the plasma generation chamber 34enters into the tubular bodies 60 a and 60 b from various directionsrelative to their axes. Then, the plasma gas is guided through thetubular bodies 60 a and 60 b towards the depressurization chamber 50while reflecting and swirling inside the tubular bodies 60 a and 60 b,and then it is discharged from the tubular bodies 60 a and 60 b into thedepressurization chamber 50.

The plasma gas enters into the tubular bodies 60 a and 60 b from variousdirections and reflects on the inner walls of the respective tubularbodies 60 a and 60 b in various directions. Therefore, the gas moves invarious directions at the opening ends of respective tubular bodies 60 aand 60 b. However, the gas discharged from the opening ends is releasedfrom the guide of the tubular body 60, so that the gas movessubstantially straight ahead in the same direction as is discharged.

Some of the plasma gas discharged from the opening ends of therespective tubular bodies 60 a and 60 b may move in substantiallyparallel with the surface of the opening end of each tubular body.

Therefore, a diameter and a length of the diffuser 58 are set in such amanner that the extensions of the respective axis of the respectivetubular bodies 60 a and 60 b intersect with the ends of the substrate 52and the extensions of the surfaces of the opening ends of the respectivetubular bodies intersect the center part of the substrate 52. It ispreferable that the diameter and the length of the diffuser 58 are setin such a manner that the areas which are exposed to the plasma gasdischarged from the respective tubular bodies 60 a and 60 b overlap atthe center part. Thus, even if the axes of the tubular bodies 60 a and60 b and the opening ends substantially perpendicularly intersect eachother, the whole area of the substrate 52 can be exposed to the plasmagas.

In order to check an advantage of the apparatus of the presentinvention, various disc diffusers with a diameter of 150 mm, in whichmany holes are formed concentrically, were prepared. It was found outthat the plasma current is 0.07 mA or less when the hole diameter is 3mm or less, and the plasma current is about 1.2 mA when the holediameter is 5 mm or 10 mm. Therefore, a diffuser with holes of 10 mm indiameter is used for making comparison with the diffuser to be used inthe apparatus of the present invention. In the diffuser 58 to be used inthe apparatus of the present invention, two tubular bodies 60 a and 60 bof 50 mm in diameter are used, one end side of the tubular body 60 is inintimate contact with one end side of the tubular body 60 b, therespective axes of the tubular bodies 60 a and 60 b perpendicularlyintersect each other, and axial lengths from this intersecting point toother end sides of the tubular bodies 60 a and 60 b are defined as 200mm.

The plasma generation chamber 34 is 80 mm in outer diameter, a tubularbody with a diameter of 150 mm and with a height of 40 mm is connectedonto the plasma inlet 34 b within the depressurization chamber 50, andeach diffuser is connected to the upper end of the tubular body. Thesubstrate 52 is attached horizontally to the bottom surface of thedepressurization chamber 50 in such a manner that the height of thesubstrate 52 is adjustable. For example, the substrate 52 having a sizeof 325×465 mm is placed at a height of 400 mm.

FIG. 2 shows a film thickness of the functional organic film (in a rangefrom the center toward the edges of the substrate 52) that is formed onthe substrate 52 under the above-described conditions. The thickness ofthe film that is formed by using the disc diffuser (which is a diffuserfor comparison with the diffuser to be used in the present invention) ischanged from 1,330 nm to 780 nm from the center toward the respectiveedges of the substrate. Thus, the difference in thickness between thecenter and the respective edges is 550 nm. In this case, the distancefrom the center toward the respective edges of the substrate is 215 mm.Thus, the film is the thickest at its center and gradually becomesthinner toward the edges. The thickness of the film is dramaticallydecreased at a position about 170 nm or more apart from the center. Thethickness uniformity of the film over the entire substrate is about 45%and thus the thickness of the film varies widely.

On the contrary, in the apparatus of the present invention, thethickness of the film is kept between 680 nm±10 from the center parttoward the edges of the substrate. The thickness of the film isdecreased from 670 nm to 550 nm in a range of 30 mm around theperipheral surface of the substrate. Thus, the difference in thicknessis 130 nm. The thickness uniformity of the film over the entiresubstrate is bout 4.6%, and therefore, variations in thickness can beminimized.

In the plasma treatment apparatus according to the present invention,the plasma gas can be substantially uniformly applied to a largesubstrate from its center to its edges. Therefore, it is possible toform an organic film of substantially uniform thickness from its centertoward its edges.

Therefore, in the plasma treatment apparatus of the present invention,where the anode electrodes formed on the substrates are cleaned and thenthe functional organic film is formed on the cleaned anode electrodes,cleaning of the surfaces of the electrodes formed on the substrate andforming the functional organic film on the electrode surfaces aresequentially carried out using a single apparatus, and thus operatingefficiency can be improved.

Further, although the conductive thin films which function as theelectrodes on the substrate are formed on portions of the coating resinand therefore O₂-plasma gas for cleaning the electrodes is exposed notonly to the surfaces of the electrodes but also to the surface of thecoating resin, the plasma gas generated in the plasma generation chamber34 passes through the diffuser 58 and is diffused in thedepressurization chamber 50. In this way, the surfaces of the electrodescan be cleaned without damaging the coating resin. Moreover, since thesmoothness of the coating resin is maintained, a display unit having nodark spots, an excellent display quality, and a high reliability can berealized.

Further, according to the apparatus of the present invention, even ifthe substrate 52 is upsized so as to use it for a large display unit orthe like, the entire surface of the substrate can be uniformly treated,and there is no difference in display quality between the center and theedges of the substrate. Therefore, the present invention can minimizevariations in quality and can realize a serious cost reduction.

In the diffuser 58 according to the above-described embodiment, theangles of inclination of the tubular bodies 60 a and 60 b are set at 45degrees. When the height of the substrate 52 is kept constant and theangles of the inclination of the tubular bodies are set at 45 degrees orless, a larger substrate can be treated as the inclination angles aresmaller. However, the center part of the substrate is likely to beinsufficiently cleaned and the film cannot be formed sufficiently. Thus,the substrate may not be treated uniformly. Alternatively, when theangles of inclination of the tubular bodies are set at 45 degrees ormore, a larger substrate cannot be treated as the inclination angles arelarger. In addition, since the opening ends of the two tubular bodiesare close to each other, the center part of the substrate isdouble-treated by the two tubular bodies and thus treated too much.Therefore, it is preferable that the angles of the inclination of thetubular bodies 60 a and 60 b are set at 20 to 70 degrees. The diameterand the length of each tubular body may be set in accordance with theinclination angle.

In the aforementioned embodiment, an angle between the axis and theopening end of each tubular body is set at 90 degrees (or 45 degreesrelative to the substrate 52) when the inclination angle of each tubularbody is 45 degrees. However, this angle may also vary in accordance withthe inclination angle of each tubular body. As shown in FIG. 3, in anarea 52 a which ranges from the center part of the substrate 52 to theoutside ends thereof, assume that an opposite area from the tubular body60 a is an area 52 b and a surface which intersects the area 52 b is avirtual surface P. A surface of the tubular body 60 a which isintersected by the virtual surface P can be defined as the opening endof the tubular body 60 a. When the inclination angle of the tubular body60 a is 45 degrees, the opening end of the tubular body is inclined atabout 45 degrees relative to the substrate 52. However, when theinclination angle of the tubular body 60 a is less than 45 degrees, theopening end of the tubular body 60 a is inclined at less than 45 degreesto the substrate 52. Thus, as the inclination angle is smaller, theopening end becomes closer to horizontal to the substrate 52. When theinclination angle of the tubular body 60 a is more than 45 degrees, theopening end of the tubular body 60 a is inclined at more than 45 degreesto the substrate 52. Therefore, as the inclination angle is larger, theopening end becomes closer to vertical to the substrate. The opening endof the tubular body 60 a may be formed not only in a manner that theentire surface of the opening end contacts the virtual surface P butalso in a manner that a portion of the opening end contacts the virtualsurface P.

In the aforementioned embodiment, two tubular bodies 60 a and 60 b whoseboth ends are the same in diameter are used as the diffuser 58. However,as the tubular bodies 60 a and 60 b, a tubular whose both ends aredifferent in diameter can also be used. In this case, if the opening endwith a larger diameter is located at the plasma inlet 34 b's side andthe opening end with a smaller diameter is located at thedepressurization chamber 50's side, the plasma gas can be morecomplicatedly moved in the diffuser 58, and therefore, preferablediffusion of the plasma gas can be obtained in the depressurizationchamber 50. Alternatively, if the opening end with a smaller diameter islocated at the plasma inlet 34 b's side and the opening end with alarger diameter is located at the depressurization chamber 50's side,the adhesion of the organic film material to the inner walls of thetubular body 60 a and 60 b can be reduced.

In the aforementioned embodiment, two tubular bodies 60 a and 60 b arearranged in a substantial V shape or a substantial Y shape. However, thenumber of the tubular body may be two or more. Alternatively, forexample, as shown in FIG. 4, two conical plates 72 and 74 may bearranged parallel to each other. In this case, a space between theconical plates 72 and 74 are used as a path of plasma gas. A vertex ofthe conical plate 72 is cut off so as to connect the plate 72 to theplasma inlet 34 b. The distance between the conical plates 72 and 74 iskept constant by a support post 76. By using a thin rod as the supportpost 76, the plasma gas can be fed to the depressurization chamber 50 inall directions. Alternatively, by using a quadrant rod as the supportpost 76, an opening area of the plasma inlet and the direction that theopening of the plasma inlet faces can be restricted. The tubular bodies60 a and 60 b may be not only a cylindrical body but also a polygonaltubular body.

In the aforementioned embodiment, the cleaning of the member to beplasma-treated and the forming of the organic film are successivelycarried out by changing material gas for plasma. However, the apparatusof the present invention can also be applied to only one of theoperations: cleaning of the member to be plasma-treated or forming ofthe organic film. Further, the member to be plasma-treated is notlimited to an in-process substrate to be used for an OLED display, butit can be a any member which requires the cleaning operation or theorganic film forming operation.

While the embodiments of the present invention have thus been describedwith reference to the drawings, it should be understood that the presentinvention is not limited to the aforementioned embodiments. Variouschanges, modifications, and improvements can be made to the embodimentson the basis of knowledge of those skilled in the art without departingfrom the scope of the present invention. This application claimspriority from Japanese Patent Application No. 2003-302815, which isincorporated herein by reference.

1. A plasma treatment apparatus comprising: a plasma generation chamber for activating gas supplied thereto so as to generate plasma; a depressurization chamber connected to the plasma generation chamber and accommodating a member to be plasma-treated; and a diffuser for guiding the plasma in a direction inclined to a gas flow path of the plasma generation chamber and for introducing the plasma into the depressurization chamber while diffusing the plasma in the depressurization chamber, said diffuser provided at a joint part of the plasma generation chamber and the depressurization chamber.
 2. The plasma treatment apparatus according to claim 1, wherein said diffuser is composed of a plurality of tubular bodies, and one end side of each tubular body is in intimate contact with one end side of another tubular body and is connected to the plasma generation chamber, while the other end sides of the respective tubular bodies are separated from each other.
 3. The plasma treatment apparatus according to claim 1, wherein an angle between an opening end which is opened in the depressurization chamber and an axis of each tubular body is determined in accordance with an angle of inclination of each tubular body.
 4. The plasma treatment apparatus according to claim 1, wherein said tubular body is cylindrically shaped.
 5. A surface treatment apparatus, comprising: a plasma generation chamber for activating gas supplied thereto so as to generate plasma; a depressurization chamber connected to the plasma generation chamber and accommodating a substrate with a conductive thin film and an organic thin film formed on a main surface thereof; and a diffuser for guiding the plasma in a direction inclined to a gas flow path of the plasma generation chamber and for introducing the plasma into the depressurization chamber while diffusing the plasma in the depressurization chamber, said diffuser provided at a joint part of the plasma generation chamber and the depressurization chamber, wherein a surface of the conductive thin film formed on the substrate is treated using different gas plasma by successively feeding different material gases to the plasma generation chamber. 